Alloy



' nature in considerable Pa tented Dec. 20, 1938 Arthur W. Peterson, signor to Metals tleboro, Mass.,-- at AMY North Attleboro, Mass., as- & Controls Corporation, Atcorporation of Massachusetts No Drawing. Application Au Serial No. 226,328

gust23, 1938,

5 Claims. (01. 75-134) sequently, it has been somewhat of a problem to This invention relates to .alloys, and with regardto certain more specific features, to gold alloys.

This application is in part a continuation of my copending application Serial No. 191,971, filed February 23, 1938, now Patent No. 2,141,156, dated December 20, 1938 and likewise entitled Alloy.

Among the several objects of the invention may be noted the provision ofa gold alloy which may be used to manufacture either so-called solid gold objects or gold-plated objects, which gold alloy will wear longer than other gold alloys of similar karats and colors, when subjected to the wear normally encountered by articles of jewelry that are worn on the hands and wrists, etc., or clothing, the provision of a gold alloy which has an exceedingly fine, close grain, which lineness and closeness of grain make much easier .the manufacture of articles from the alloy, and prevent what is known as "orange peel '(surface roughness caused by abnormally large crystals of metal being set in relief by mechanical working of the metal such as bending and other manufacturing operations) during the manufacture of articles of jewelry from the gold alloy; the provision of a gold alloy which may be usedeither as solid gold or as gold plate which has much greater resistance to tarnish and corrosion encountered in atmospheric conditions and in perspiration acids, etc.; and the provision of a gold alloy which, hardness for hardness, is adapted to higher annealing and soldering temperatures in the manufacture of jewelry articles from it than other gold alloys now available. Other objects will be in part obvious and in part pointed out hereinafter. 1

The invention accordingly comprises the ingredients and combinations of ingredients, the proportionsthereof, and features of composition, which will be exemplified in the products hereinafter described, and the scope of the application of which will be indicated in the following claims. v

In the manufacture of plated gold articles of jewelry, one of the difflculties encountered is the provision of a gold plate which will stand up against the abrasion caused by clothing, etc.

when the article is being worn. The gold plate on such an article is generally verythin, and the life of a plated gold article is determined to a great extent by the resistance to abrasion .of the gold plate itself. It has been possible in the past to provide gold alloys of a given karat which will withstand wear to a greater degree than alloys commonly in use. This is ordinarily done by adding to the gold amounts. The eiTect on the alloy is to give it greater hardness, but the resulting color, from the standpoint of the jewelry industry, is not as good as it was before. Con

alloy metals of harderprovide shard gold alloy in a given karat which would present a color which, for the given karat of the gold, would be acceptable to the jewelry industry. The alloy which is the subject of this invention provides a metal which for a given karat and given color has much greater wear resistance than other hitherto known gold alloys of similar karat and color. It is known to the applicant, of course, that white gold, which has nickel in it, has superior resistance to tarnish and abrasion than yellow gold of like karat.

However, the base alloy described herein makes possible the manufacture of a yellow gold alloy whose resistance to wear and corrosion compares favorably with white gold.

In the manufacture of articles of jewelry from gold, it is customary in many cases to use a goldplated stock. In the subsequent bending, stretching, and shaping operations, etc., of the article, the gold plate has a tendency to present a rough crystalline appearance on the surface. This phenomenon is commonly called orange peel" in the jewelry and allied industries. It is a serious defect and great pains must be taken to prevent it in the manufacture of jewelry items. The present invention discloses an alloy which has a very fine, close grain which to a great extent prevents this'so-called orange peel. This fine, close grain is inherent in the structure, and while fine,'close grains can be obtained in other gold alloys, it is only at the expense of much mechanical working. The cobalt addition, which is a provision of this invention, prevents abnormal crystal size in the alloy. The present alloy thus provides a metal which affords in either case, cold-worked or annealed condition, a fine,

close grain.

Among the many dlfilculties encountered in the provision of gold alloys for the jewelry industry, is the difficulty of tarnish and corrosion of the gold by atmospheric conditions and by the acids commonly present in the perspiration of individuals. For example, in the optical goods industry, it is no uncommon occurrence to receive complaints from customers regarding the fact that various parts of their spectacle frames have become eaten away on the surface by the skin acids, with resulting roughness and raggedness of' the metal, which in turn causes skin irritation where it comes in contact with the skin. This is caused by the fact that the perspiration acids have eaten away the gold plate which covers a" plated spectacle frame. This destruction of the gold plate is a very common occurrence in all gold-plated articles of contact with the skin of the wearer. One of the solutions in the past has been to substitute a gold alloy for the plate which has a richer gold content. This is a necessarily expensive procejewelry which come in i the manufacturing processes.

dure and. one that it is desired to avoid. The gold alloy which is .the subject of the present invention provides a metal which has greater tarnish and corrosion resistance to skin acids,

course of manufacture, to submit the article to either high annealing temperatures or high 501- dering temperatures. This tendency of hitherto known gold alloys of. similar'color has been for the alloys to soften unduly with this treatment, creating distortion and too great flexibility in the finished article. For example, in the manufacture of watch cases, which are made of very thin material (relatively speaking), at one stage of the manufacture the watch cases must be annealed, and at another point they must have the hinges soldered on. One difficulty that has been encountered is that the watch case itself will buckle due to stresses in the metal being relieved too unevenly. Furthermore, the finished watch case will be so soft that in its use, it is apt to twist and distort in shape, thus causing misalignment of parts and possibly damage to the contained delicate mechanism. Furthermore, many gold or gold-plated articles of desirable color for their karat, wear excessively in use. This is caused by softness in the finished article caused by necessary annealing operations during The present gold alloy is one that provides a metal which is adapted (for given hardness) to higher annealing and soldering temperatures. For example, if the watch case mentioned above were to be annealed at, say, 800 F., it would come out with a certain softness. If the same watch case is made out of the gold alloy which is the subject of this invention, and is subjected .to the same annealing temperature, the resulting case will be harder temper than in the former case. This means, of course, that the metal has more springiness and consequently more resistance to bending and buckling.

It will also wear longer, an important desidera- .tum.

The gold alloy of the present invention consists basically of gold, copper, cobalt, silver, and zinc or cadmium.

The gold content depends upon the desired karat of the gold. The. present invention relates principally to alloys within the karat range of 8 to 20; hence the proportion of gold in the alloy, by weight, may vary from about 33% to about 84=%.

The copper content may vary from about 10.7% to about 67%, by weight, of the alloy, depending upon the color, hardness, and other qualities desired of the alloy. Less than 10.7% copper ordinarily produces an unsatisfactory alloy.

The cobalt content may vary from'about 0.1% to about 5%, by weight, of the alloy, about 1% being usually preferred. The cobalt, possibly in combination with the copper present, seems to act as the regulator of grain size in the alloy.

If no cobalt is used, the grain sizeof the alloy which behaves similarly to zinc) likewise stifiens the alloy., The silver content affects the mal-' leability of the alloy.

made in accordance with the teachings of the present invention. Alloy A is given primarily for comparative purposes.

Composition .in per cent. by weight Alloy Karat Gold Copper Cobalt Silver Zinc 10 41. 67 41. 06 None 7. 67 8. 7 10 41. 67 41.13 1. 0 7. 5 8. 7 8 33.0 47, 4 1.0 8. 6 10.0 20 84. 0 10. 7 1. 0 2. 0 2. 3

Each of the above alloys A, B and C was then rolled and annealed with identical schedules. All anneals were for 40 minutes at 1200 F. All re-' ductions in rolling were 50% in'the thickness.

The following table gives the hardness measure-' ments (Vickers No. 5 and Rockwell B) for each alloy measured, in thicknesses of 0.060 and 0.030 inch, in both hard and annealed conditions:

li'he following table gives the results obtained upon testing the 0.030 inch thick annealed alloys for properties such as orange peel and grain structure:

Alloy Appearance of a 5 m. m. Grain size ERICHSEN cur millimelz-rs Very coarse orange peel. 0 12 Very smooth and silky About 0,007 Smooth and fine 0.010 to 0.015 Very smooth and silky About 0.005

The superiority of the alloys made'in accordance with the present invention (B, C and D) to the typical prior art alloy- (A) is evident.

In general, the best procedure for making up the alloys of the present invention is first to make a base alloy containing the copper and supplementary metals, if any, then to modify said base alloy by adding thereto the correct amount of cobalt, and finally to alloy the cobalt-containing base alloy with fine gold. For example, to make up alloy 13, which is a commercially preferred type of the present invention, a first base alloy is made up of about 71.7% coppenabout 13.1% silver, and about 15.2% zinc. To about 98.3% of this first base-alloy is added about 1.7% of cobalt to get a second base alloy. The second base alloy then is made up of about 70% copper, 13% silver, 15% zinc, and 2% cobalt. To 58.3% of the second base alloy is then added about 41.7% of fine gold, thus to obtain the desired final alloy. The aforesaid base alloy of copper, silver, zinc, andcobalt is claimed in my said application Serial No. 191,171. 1

The efiect of increasing the cobalt content is to produce a paler gold (the'decolorizing effect, or

tendency to give the resulting alloy a finer. closer grain if the cobalt content is increased. The effr ct on the melting point of the final gold alloy of increase of cobalt is to" raise the melting point.

In view of the above, it will be seen that the several objectsof the invention are achieved and other advantageous results attained.

As many changes could be made in the above alloys without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted-as illustrative and not in a limiting sense.

I claim:

1. A gold alloy consisting of about 33 to 84% gold, 10.7 to 67% copper, 0.1 to 5% cobalt, 2 to 10% silver, and 2 to10% zinc.

2. A gold alloy composed of the following metals in about the stated proportions:

Per cent Gold 41.67 Copper 41.13 Cobalt 1.0 Silver I 7.5 Zi 8.7

3. A gold alloy composed of the following metals in about the stated proportions:

; Per cant Gold 33.0 Copper 47.4 Cobalt 1.0 Silver 8.6 Zinc 10.0

4. A gold alloy composed of the following metals 5. A gold alloy consisting of about 33 to 84% gold, 10.7 to 50% copper, 0.3 to 1.4% cobalt, 2 to 9% silver, and 2 to 10% zinc.

AR'I'HUR W. PETERSON. 

